Once upon a time pumpjack units were installed wherever needed with little or no regard to animal and plant life which had to co-exist therewith. The pumpjack units seldom were painted, crude oil escaping from packing boxes contaminated the immediate area, and if someone or some animal happened to walk or drive into the massive operating machinery, they were admonished and told that they should exercise greater caution. Occasionally, when a pumpjack unit was located directly on a school yard, or in the middle of a street, the owners occasionally would fence off the pumpjack unit as a feeble gesture of their concern over the mechanical monster they had imposed upon society.
But times are changing, and nowadays it is not unusual for pumpjack units to be neatly painted, surrounded by a protective fence, and the leakage from the packing boxes and piping greatly reduced or almost eliminated.
There are many occasions where the physical size of a pumpjack unit is objectionable to the immediate environment. For example, where the borehole has been formed near parks, in recreational facilities, and in crowded areas such as cities and towns, and more especially in a field of vegetation which is irrigated by a traveling irrigation system. It is not always the visual observation of the pumpjack unit which is objectionable, because some pumpjack units are a work of art and a beauty to behold; rather, it is the interference of the monster respective to the conduct of our daily lives.
In an irrigation field, which utilizes a traveling irrigation system, the presence of any tall obstruction, such as a pumpjack unit, prevents the irrigation system from making a complete circle or cycle. In these instances, it has heretofore been necessary for the downhole pump to be actuated by apparatus other than a pumpjack unit because the extreme elevation of the Sampson post, walking beam, and horsehead prevented the traveling irrigation system from passing over the pumpjack unit.
In a pumpjack unit, as the pitman arm is reciprocated by the crank, the walking beam is oscillated or rocked about the Sampson post bearing, causing the horsehead to move within an arc having a radius drawn from the Sampson post bearing.
The outermost side of the horsehead is configurated into a segment of a circle which coincides with the arc drawn by the horsehead when oscillatory motion is imparted thereinto by the walking beam, so that the bridle cable supported by the circumferentially extending part of the track located on the outermost side of the horsehead is moved vertically. This complex motion causes the hanger bar located on the lower end of the cable to be stroked in a vertical plane and along the longitudinal axial centerline of the borehole. In the prior art, it is customary to make the length of the core of the arc described by the outermost side of the horsehead somewhat longer than the stroke imparted into the polish rod.
The bridle usually is connected to the polish rod by a hanger bar and rod clamp, all of which is customarily suspended below the horsehead and above the stuffing box of the well. The vertical distance required by the prior art horsehead, bridle, hanger bar, and rod clamp is of considerable length and often extends up into the air 10-15 feet.
Applicant has discovered that the maximum height of the pumpjack unit can be reduced to a value under 5 feet, by placing the pumpjack unit below ground level, and by placing the stuffing box of the wellhead below ground level, and by shortening the overall vertical height of the horsehead to a value slightly less than the length of a rod stroke so that the bridle moves laterally to and fro a small amount at each end of the stroke thereof. This unexpected phenomena enables a significant reduction in the overall vertical dimension of the horsehead.
Applicant has also discovered that a horsehead can be fabricated to enclose the rod clamp during reciprocation of the bridle and polish rod, thereby effecting still another unexpected reduction in the vertical height requirement of a pumpjack unit.
When all of the these unobvious and unexpected savings in height are accumulated, the result is a pumpjack unit of unusually low profile which finds acceptability in many locations where conventional pumpjacks were heretofore refused.
Moreover, when the above novel improvements are effected, the resultant structure provides unexpected safety features which enhance the ease with which maintenance can be effected on the pumpjack unit.
A pumpjack unit having a low profile and located partially below the surface of the earth in order to overcome the foregoing objections is the subject of the present invention.